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11#include <crypto/skcipher.h>
12#include <keys/encrypted-type.h>
13#include <keys/user-type.h>
14#include <linux/random.h>
15#include <linux/scatterlist.h>
16#include <uapi/linux/keyctl.h>
17
18#include "ext4.h"
19#include "xattr.h"
20
21static void derive_crypt_complete(struct crypto_async_request *req, int rc)
22{
23 struct ext4_completion_result *ecr = req->data;
24
25 if (rc == -EINPROGRESS)
26 return;
27
28 ecr->res = rc;
29 complete(&ecr->completion);
30}
31
32
33
34
35
36
37
38
39
40static int ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
41 char source_key[EXT4_AES_256_XTS_KEY_SIZE],
42 char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
43{
44 int res = 0;
45 struct skcipher_request *req = NULL;
46 DECLARE_EXT4_COMPLETION_RESULT(ecr);
47 struct scatterlist src_sg, dst_sg;
48 struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
49
50 if (IS_ERR(tfm)) {
51 res = PTR_ERR(tfm);
52 tfm = NULL;
53 goto out;
54 }
55 crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
56 req = skcipher_request_alloc(tfm, GFP_NOFS);
57 if (!req) {
58 res = -ENOMEM;
59 goto out;
60 }
61 skcipher_request_set_callback(req,
62 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
63 derive_crypt_complete, &ecr);
64 res = crypto_skcipher_setkey(tfm, deriving_key,
65 EXT4_AES_128_ECB_KEY_SIZE);
66 if (res < 0)
67 goto out;
68 sg_init_one(&src_sg, source_key, EXT4_AES_256_XTS_KEY_SIZE);
69 sg_init_one(&dst_sg, derived_key, EXT4_AES_256_XTS_KEY_SIZE);
70 skcipher_request_set_crypt(req, &src_sg, &dst_sg,
71 EXT4_AES_256_XTS_KEY_SIZE, NULL);
72 res = crypto_skcipher_encrypt(req);
73 if (res == -EINPROGRESS || res == -EBUSY) {
74 wait_for_completion(&ecr.completion);
75 res = ecr.res;
76 }
77
78out:
79 skcipher_request_free(req);
80 crypto_free_skcipher(tfm);
81 return res;
82}
83
84void ext4_free_crypt_info(struct ext4_crypt_info *ci)
85{
86 if (!ci)
87 return;
88
89 if (ci->ci_keyring_key)
90 key_put(ci->ci_keyring_key);
91 crypto_free_skcipher(ci->ci_ctfm);
92 kmem_cache_free(ext4_crypt_info_cachep, ci);
93}
94
95void ext4_free_encryption_info(struct inode *inode,
96 struct ext4_crypt_info *ci)
97{
98 struct ext4_inode_info *ei = EXT4_I(inode);
99 struct ext4_crypt_info *prev;
100
101 if (ci == NULL)
102 ci = ACCESS_ONCE(ei->i_crypt_info);
103 if (ci == NULL)
104 return;
105 prev = cmpxchg(&ei->i_crypt_info, ci, NULL);
106 if (prev != ci)
107 return;
108
109 ext4_free_crypt_info(ci);
110}
111
112int _ext4_get_encryption_info(struct inode *inode)
113{
114 struct ext4_inode_info *ei = EXT4_I(inode);
115 struct ext4_crypt_info *crypt_info;
116 char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
117 (EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1];
118 struct key *keyring_key = NULL;
119 struct ext4_encryption_key *master_key;
120 struct ext4_encryption_context ctx;
121 const struct user_key_payload *ukp;
122 struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
123 struct crypto_skcipher *ctfm;
124 const char *cipher_str;
125 char raw_key[EXT4_MAX_KEY_SIZE];
126 char mode;
127 int res;
128
129 if (!ext4_read_workqueue) {
130 res = ext4_init_crypto();
131 if (res)
132 return res;
133 }
134
135retry:
136 crypt_info = ACCESS_ONCE(ei->i_crypt_info);
137 if (crypt_info) {
138 if (!crypt_info->ci_keyring_key ||
139 key_validate(crypt_info->ci_keyring_key) == 0)
140 return 0;
141 ext4_free_encryption_info(inode, crypt_info);
142 goto retry;
143 }
144
145 res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
146 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
147 &ctx, sizeof(ctx));
148 if (res < 0) {
149 if (!DUMMY_ENCRYPTION_ENABLED(sbi))
150 return res;
151 ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
152 ctx.filenames_encryption_mode =
153 EXT4_ENCRYPTION_MODE_AES_256_CTS;
154 ctx.flags = 0;
155 } else if (res != sizeof(ctx))
156 return -EINVAL;
157 res = 0;
158
159 crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL);
160 if (!crypt_info)
161 return -ENOMEM;
162
163 crypt_info->ci_flags = ctx.flags;
164 crypt_info->ci_data_mode = ctx.contents_encryption_mode;
165 crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
166 crypt_info->ci_ctfm = NULL;
167 crypt_info->ci_keyring_key = NULL;
168 memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
169 sizeof(crypt_info->ci_master_key));
170 if (S_ISREG(inode->i_mode))
171 mode = crypt_info->ci_data_mode;
172 else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
173 mode = crypt_info->ci_filename_mode;
174 else
175 BUG();
176 switch (mode) {
177 case EXT4_ENCRYPTION_MODE_AES_256_XTS:
178 cipher_str = "xts(aes)";
179 break;
180 case EXT4_ENCRYPTION_MODE_AES_256_CTS:
181 cipher_str = "cts(cbc(aes))";
182 break;
183 default:
184 printk_once(KERN_WARNING
185 "ext4: unsupported key mode %d (ino %u)\n",
186 mode, (unsigned) inode->i_ino);
187 res = -ENOKEY;
188 goto out;
189 }
190 if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
191 memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
192 goto got_key;
193 }
194 memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
195 EXT4_KEY_DESC_PREFIX_SIZE);
196 sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE,
197 "%*phN", EXT4_KEY_DESCRIPTOR_SIZE,
198 ctx.master_key_descriptor);
199 full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
200 (2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0';
201 keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
202 if (IS_ERR(keyring_key)) {
203 res = PTR_ERR(keyring_key);
204 keyring_key = NULL;
205 goto out;
206 }
207 crypt_info->ci_keyring_key = keyring_key;
208 if (keyring_key->type != &key_type_logon) {
209 printk_once(KERN_WARNING
210 "ext4: key type must be logon\n");
211 res = -ENOKEY;
212 goto out;
213 }
214 down_read(&keyring_key->sem);
215 ukp = user_key_payload(keyring_key);
216 if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
217 res = -EINVAL;
218 up_read(&keyring_key->sem);
219 goto out;
220 }
221 master_key = (struct ext4_encryption_key *)ukp->data;
222 BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE !=
223 EXT4_KEY_DERIVATION_NONCE_SIZE);
224 if (master_key->size != EXT4_AES_256_XTS_KEY_SIZE) {
225 printk_once(KERN_WARNING
226 "ext4: key size incorrect: %d\n",
227 master_key->size);
228 res = -ENOKEY;
229 up_read(&keyring_key->sem);
230 goto out;
231 }
232 res = ext4_derive_key_aes(ctx.nonce, master_key->raw,
233 raw_key);
234 up_read(&keyring_key->sem);
235 if (res)
236 goto out;
237got_key:
238 ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
239 if (!ctfm || IS_ERR(ctfm)) {
240 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
241 printk(KERN_DEBUG
242 "%s: error %d (inode %u) allocating crypto tfm\n",
243 __func__, res, (unsigned) inode->i_ino);
244 goto out;
245 }
246 crypt_info->ci_ctfm = ctfm;
247 crypto_skcipher_clear_flags(ctfm, ~0);
248 crypto_tfm_set_flags(crypto_skcipher_tfm(ctfm),
249 CRYPTO_TFM_REQ_WEAK_KEY);
250 res = crypto_skcipher_setkey(ctfm, raw_key,
251 ext4_encryption_key_size(mode));
252 if (res)
253 goto out;
254 memzero_explicit(raw_key, sizeof(raw_key));
255 if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) {
256 ext4_free_crypt_info(crypt_info);
257 goto retry;
258 }
259 return 0;
260
261out:
262 if (res == -ENOKEY)
263 res = 0;
264 ext4_free_crypt_info(crypt_info);
265 memzero_explicit(raw_key, sizeof(raw_key));
266 return res;
267}
268
269int ext4_has_encryption_key(struct inode *inode)
270{
271 struct ext4_inode_info *ei = EXT4_I(inode);
272
273 return (ei->i_crypt_info != NULL);
274}
275
